Vehicles such as automobiles are provided with electric components such as headlights, car security devices, etc. The electric components are supplied with electric power from a vehicle battery for operation. For example, Patent Document 1 shows in the drawings a car security device. According to the description of Patent Document 1, the car security device is normally supplied with electric power from a main power supply (vehicle battery). When the electric power from the main power supply is not supplied to the car security device, the car security device is supplied with electric power from a chargeable battery (standby battery) via a power switching unit.
The vehicle battery can start a motor of the vehicle and hence is an important part or component. However, since the vehicle battery is also able to supply electric power to various electric components as described above, the residual capacity of the vehicle battery decreases depending on the operating state (using state) of each individual electric component. When the residual capacity of the vehicle battery is low, the motor of the vehicle is not started. In other words, the vehicle battery may become dead according to the operating state (using state) of the electric components.
Patent Document 1 also describes that vibration is detected by a sensor. However, when determining whether the vehicle has been stolen or not based on the presence/absence of vibration, if vibration is produced, for example, by a cat jumped on an engine, it may occur that a theft of the vehicle is erroneously determined even when the situation is not a vehicle theft actually. Such erroneous determination of the vehicle theft made especially at night will bother neighborhood due to alarm noise.